What is the difference between a repetition and replication

Repetition is when you make more than once a measurement in a sample.

Replication is when you make a measurement a more than one sample.

Explanation:

For example: I have to determine the average weight of beakers. If I weigh 3 times the same beaker, I am doing repetitions (measurements in the same sample). Whit repetitions I can only stimate the measurement instrument error (in this case the error of the used balance).

If I take 3 beakers and weigh them, I have 3 different weigh measurements. These measurements are replicates (measurements in more than one sample). With replicates I can stimate the experiment error (the error associated to the real weight of the beakers).

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2